The subject matter disclosed herein relates to an X-ray CT (computed tomography) apparatus and a method of generating an image, more specifically to an X-ray CT apparatus which makes use of two types of X-ray having different energy to take images with one of two materials within a subject to be examined being fractionated, and a method of generating an image for the use of such X-ray CT apparatus.
When taking images of a specific material fractionated, i.e., MD (material decomposition) images with an X-ray CT apparatus, two types of X-ray which have different energy are used. The scan by means of two types of X-ray each having different energy is also referred to as a dual energy scan.
Because of the energy characteristics of the X-ray absorption coefficient, the data obtained with lower energy X-ray has a value different from the data obtained with higher energy X-ray, and the data ratio will be different according to the material. This characteristic of the X-ray absorption coefficient is made use for taking MD images (for example see JP-A-2004-65975 Japanese Patent Application No. 2004-065975 (paragraphs 0019 to 0023, FIGS. 3 and 4)).